Semiconductor device manufacturing principally involves two complex processes, die fabrication and device packaging. Problems associated with any of the two processes may cause the integrated circuit (IC) on the die to malfunction. Failure analysis is an important step in IC production for the purpose of identifying defects in a fabricated die, deducing causes for such defects and coming up with corresponding solutions. As a precondition of failure analysis, a die needs to be removed intact from the package that encases the die before taking any further analytical steps, e.g., parallel lapping and cross-sectioning.
Conventionally, a die is removed from its plastic package through a chemical approach. For example, a die and its plastic package may be submerged in a solvent comprising 50% nitric acid and 50% water. The package material, e.g., a phenol-based compound, reacts with the nitric acid and is then completely dissolved in the solvent. However, since those materials that constitute the die do not react with the solvent, the die itself remains intact. The die is then removed from the solvent and rinsed several times with water to clear away any residual solvent and/or package material from its surface.
There are several issues with this conventional approach. First, the nitric acid solvent is hazardous and an operator needs to be extremely careful and wear protective clothing and gloves during the die removal operation. Second, this approach is time consuming. It takes at least an hour for the package to be completely dissolved and the die to be rinsed and dried.
In view of the aforementioned problems, it would be desirable to develop a die removal method that is both safer and more efficient.